Adaptive Modulation Method, Radio Network Controller, and Mobile Communication System

1. An adaptive modulation method for use in a mobile communication system employing a TDMA scheme, the method comprising the steps of: associating a modulation scheme with each time slot within a frame, each time slot being associated with a same modulation scheme in plural frames; and modulating transmission data of a communication channel using the modulation scheme associated with the time slot to which the communication channel is assigned.

2. The adaptive modulation method as claimed in claim 1 , the method further comprising the step of: changing the modulation scheme associated with each time slot to change the modulation scheme applied to each communication channel.

3. The adaptive modulation method as claimed in claim 2 , the method further comprising the steps of: monitoring line quality in each communication channel; and changing the modulation scheme applied to each communication channel such that the modulation scheme having more bits per symbol is applied to the communication channel the better the line quality of the communication channel is.

4. The adaptive modulation method as claimed in claim 1 , the method further comprising the step of: changing an assignment of the time slots to the communication channels to change the modulation scheme applied to each communication channel.

5. The adaptive modulation method as claimed in claim 4 , the method further comprising the steps of: monitoring line quality in each communication channel; and changing the modulation scheme applied to each communication channel such that the modulation scheme having more bits per symbol is applied to the communication channel the better the line quality of the communication channel is.

6. A mobile communication system employing a TDMA scheme, the system comprising: a part for associating a modulation scheme with each time slot within a frame, each time slot being associated with a same modulation scheme in plural frames; and a part for modulating transmission data of a communication channel using the modulation scheme associated with the time slot to which the communication channel is assigned.

7. The mobile communication system as claimed in claim 6 , the system further comprising: a part for changing individually the modulation scheme associated with each time slot within a frame to change individually the modulation scheme applied to each communication channel.

8. The mobile communication system as claimed in claim 7 , the system further comprising a part for monitoring line quality in each communication channel, wherein: the part for changing the modulation scheme changes the modulation scheme applied to each communication channel on the basis of the line quality obtained by the part for monitoring the line quality such that the modulation scheme having more bits per symbol is applied to the communication channel the better the line quality of the communication channel is.

9. The mobile communication system as claimed in claim 6 , the system further comprising: a part for changing an assignment of the time slots to the communication channels to change the modulation scheme applied to each communication channel.

10. The mobile communication system as claimed in claim 9 , the system further comprising a part for monitoring line quality in each communication channel, wherein: the part for changing the assignment of the time slots changes the modulation scheme applied to each communication channel on the basis of the line quality obtained by the part for monitoring the line quality such that the modulation scheme having more bits per symbol is applied to the communication channel the better the line quality of the communication channel is.

11. A radio network controller that is provided in a mobile communication system employing a TDMA scheme and assigns communication channels to time slots, the controller comprising: a part for associating a modulation scheme with each time slot within a frame, each time slot being associated with a same modulation scheme in plural frames; and a part for modulating transmission data of a communication channel using the modulation scheme associated with the time slot to which the communication channel is assigned.

12. The radio network controller as claimed in claim 11 , the radio network controller further comprising: a part for changing individually the modulation scheme associated with each time slot within a frame to change individually the modulation scheme applied to each communication channel.

13. The radio network controller as claimed in claim 12 , the radio network controller further comprising a part for monitoring line quality in each communication channel, wherein: the part for changing the modulation scheme changes the modulation scheme applied to each communication channel on the basis of the line quality obtained by the part for monitoring the line quality such that the modulation scheme having more bits per symbol is applied to the communication channel the better the line quality of the communication channel is.

14. The radio network controller as claimed in claim 11 , the radio network controller further comprising: a part for changing an assignment of the time slots to the communication channels to change the modulation scheme applied to each communication channel.

15. The radio network controller as claimed in claim 14 , the radio network controller further comprising the part for monitoring line quality in each communication channel, wherein: the part for changing the assignment of the time slots changes the modulation scheme applied to each communication channel on the basis of the line quality obtained by the part for monitoring the line quality such that the modulation scheme having more bits per symbol is applied to the communication channel the better the line quality of the communication channel is.